Coax to BNC connection for digital

Forgot to edit..my main concerns.

Happy Holidays to all!

Thanks all for the this information. You have answered mine main concerns, regarding having a cable made, if there were adapters, and the issue as to 50 vs. 75 ohms service. I do have 75 ohm RCA cables and will will most likely look for an adapter. 

Given the DAC has BNC, should I purchase a server with BNC output I would  then just purchase a BNC cable which I suppose would need be rated for 50ohms. 

Thanks Al. The DAC I have purchased, however have not yet received, is the Mirror Audio Tubadour III. It has a BNC input along with USB, toslink, and coax. Currently the coax will serve my CD transport, toslink my DVD player, and thinking if I get a server I will use the BNC. I will verify the impedance for the BNC connection for the DAC and find a impedance matched server, when and if I follow that route.  

As an additional thought, I could use a coax output from DVD player with RCA cable and a RCA/BNC adapter as opposed to a toslink cable. Thoughts anyone?

Thanks again Al for your help! That said, I am embarrassed in that I was mistaken about the additional input being BNC when in fact it is AES. My only excuse for my confusion is that I haven't received the DAC yet, a poor platform indeed. 

So I now must explore the subject of going from a coax RCA
 output to an AES input. 

I still can't believe that in my mind I replaced the AES outlet available on the DAC with a BNC one. AT 70 I feel I am in good physical shape, however my mind may not be keeping up.  

After some exploration I believe I am best off looking for a streamer/server with AES output and use appropriate 110 ohm XLR cable. This will be a 'down the road' investment. 

Well thanks again Al!  I really appreciate the time you have offered me on this.  I dare chance some more. 

The DAC am purchasing has the AES/EBU input that I likely will want to use. Currently I have both a DVD player and a CD transport with optical and coax SPDIF outputs. I also have two 1.5 meter 75ohm RCA cables available for use. I would prefer to use these cables between both the DVD player and the CD transport and the new DAC to avoid use of the optical connection.  Obviously this is no problem for one of the two disc players however the other will have to be connected to the AES input on the DAC. 

It is the impedance issue that has me confused. I know that a XLR microphone cable lacks the proper impedance for digital use. AES when balanced is 110ohms as I understand it. I believe with my new DAC I would be using a cable in unbalanced mode at 75ohms. I guess I need to verify this with Audio Mirror. 

If one has an 75ohm RCA cable can one fit a male RCA to male XLR adapter for my needs?  How does the impedance of the adaptor affect this? Or, based on the first sentence of the wikipedia report, can one use a BNC/AES adapter at the DAC input if one has a 75 ohm RCA to BNC cable? 

Al, I am slowing down to allow my mind to keep up. :-).  I have decided that I will hook up the CD transport via RCA, and the DVD player via toslink and reserve the AES input on the DAC for a server/streamer should I purchase one.

I began a search for adaptors and in that search I came across the data link box you provided a link to. Given that I only use the DVD player for video I have decided that toslink optical will be the best approach. A single quality glass optical cable can be had at the price of this box.

Thanks once again for your help. Have a happy New Year!